This invention relates to improvements in a seed drill of the type generally disclosed in my U.S. Pat. No. 3,177,830, which was issued on Apr. 13, 1965. Modifications of this type of seed drill are disclosed in my U.S. Pat. Nos. 3,319,590, issued May 16, 1967, 3,177,830, issued Apr. 13, 1965, 3,385,243, issued May 28, 1968 and 4,844,174, issued Jul. 4, 1989. The disclosures of my four prior patents are hereby incorporated within this disclosure by reference.
The seed drills described in my referenced U.S. patents are designed for deep furrow seeding of crops. Seed is planted at the bottom of a furrow having packed sloping sides. This is accomplished by placing the seed into the slotted soil behind a shovel forward of and followed closely by press wheels that pack the sides of the open furrow. The press wheels pack the sloping sides of the furrow after seed placement in an attempt to assure accurate control of both planting depth and proper soil coverage over the seeds.
The above-referenced inventions were developed primarily for use in soil conditions where subsurface moist soil was covered by a substantial layer of dry loose soil. Such conditions are prevalent in the northwestern United States where winter wheat is grown by dry land farming techniques. While the referenced inventions have been widely adopted and have been proven to enhance seed germination and resulting crop yields when used, it is recognized that substantial variations in planting conditions continue to exist even where such improvements are used. This can be attributed to the natural variations that occur in the subsurface elevation of the moist soil and to surface undulations encountered where fields are not perfectly flat.
Under normal conditions, such planting equipment must be preset to place seed at an average depth that will normally locate it in moist soil. However, where the soil moisture line is below the average elevation for a field or where the equipment must span a slight dip in the soil contour, the planting equipment will place seeds in drier soil than is desirable. Such soil is very unstable and likely to slough downwardly to partially fill the furrow above the seed. When this occurs, expected growth from the germinating seed will be disrupted by the unwanted soil cover. This is particularly detrimental if there has been an intervening rain that forms a crust in the covering soil through which the emerging plant growth must penetrate.
Many of the problems of prior art drills, which usually required staggered placement of seed openers across the drills, were solved when an in-line version of the drill shown in U.S. Pat. No. 3,319,590 was commercially introduced. In these drills, the seed placement boot was overlapped within the following press wheels. The furrow opening boot was relatively narrow and could be effectively pulled through the field in a transverse straight line relationship of the shovel openers and press wheels.
This drill became very popular in summer-fallow areas. However, it was not without problems. It could not travel through much trash or straw when a furrow deeper than four inches was required to reach moist soil. In some of the drier areas, users were forced to revert back to staggered drills.
Later development of notched pressed wheels (U.S. Pat. No. 4,844,174) gave the in-line drills much better trash clearing capabilities, but the drills still encountered problems where five to six inches of dry soil was encountered. Under these drier conditions the pointed opener had to be able to retract rearwardly into the press wheels to clear field obstacles. It was physically impossible to design an opener of this design which could lift sufficient moist soil to form a covering over the sides of the furrows and hold the packed furrows open after seeding. In many situations three to four inches of dry soil would fall back over planted seed in the resulting deep furrows.
An ideal drill should produce a planting furrow, whether shallow or deep, with no dry dirt located over the seeds. It should be applicable to no-till seeding methods, as well as to conventional tilling techniques. Grain seeds should be positioned approximately one to two inches deep within packed moist soil with very consistent accuracy. Other types of seeds should be planted very accurately at depths ranging between one-fourth to one-half inch or even less.
Recognized shortcomings in the planting accuracy of the drills described in my prior patents have led me to the discovery of a new relationship between the planting runner for placement of seeds and the press wheels that pack the furrow sides as disclosed herein. With this new drill, because of the relative locations of the component parts in a planting sequence, each operation carried out by these component parts contributes to formation of a perfect furrow and accurate seed placement. Seed is planted in a carefully defined slot after furrow formation and packing has been completed. No uncontrolled seed coverage can occur in the packed furrow. When planting in moist soil conditions, no furrow formation is required. Use of this accurate seed placement equipment will result in substantially higher yields and eliminate or minimize the necessity of reseeding, regardless of weather encountered after the seeding sequence has been carried out.